Illuminating appliance



W. A. DOHEY. ILLUMINATING APPLIANCE. APPLICATION FILED 'MAY 3. 1917.

1,359,498, Patented'Nov. 23, 1920.

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UNITED STATES PATEN T OFFICE.

WILLIAM A. DOREY, 0F NEWARK OI-IIO, ASSIGNOR T0 I-IOLOPHAN E GLASS COMPANY, INC., 013 NEW YORK, N. Y., A CORPORATION OF NEW JERSEY.

1 ILLUMINATING APPLIANCE.

Specification of Letters Patent. Patented NOV. 23, 1920.

Application filed na a, 1917. Serial No. 166,181.

To all whom z'tmay concern: I

Be it known that I, WILLIAM A. Down, a citizen of the United States, resldlng' at Newark, in the county of Licking and State of Ohio, have invented certain new and use Improvements in Illuminating Appllances, of which the following is a specification.

The object of my invention is the forma- 1 tion of a reflector which will screen the rays from a light source to certain angles and todirect the light zones.- f v v Figure 1 is a vertical section of a reflector and li ht source showing the typical light rays of a preferred form of my invention. Fig. 2 is a bottom view of the same. Fig. 3 is an enlarged section of the prisms on a portion. of the screening plate with the thus screened into useful course of light rays shown.-

Similar lettering is used in all of the figures. G is a lightsource shown for convenience and purposes of calculation with a point source H. Thelamp axis is shown as line I. The reflector is here shown as having so-called double reflecting prisms on the surface, that is, prisms'whosesides make an apex angle of substantially 90 degrees. Any reflector having good reflecting qualities may be used, but a specular reflector, that is, one'acting mainly by mirror like reflection, is preferred. For the best results, therefore,

- the reflector must be either mirrored or of polished metal or have the above described total reflecting prisms on its surface. The

mouth of the reflector is" partially covered with. a plate 15, preferably of the, form shown in Fig. 2 having upon its outer-surface a prismatic construction F..

The operation of the device is as follows. The reflector J surrounds the light source Gr. Except where the plate E covers the open mouth of the reflector,, the light rays m, m, m" from the light source (shown as a point) are transmitted directly and by reflection and out of. the mouth of the'reflector. Light rays coming direct from the source to the plateE as D, D strike the interior of the plate, are refracted and emerge as shown in Fig. 3.

13, C, of the prisms, as shown in Fig. 3, and

,. reflected rays.

. are refracted downward by them toward the lamp axis. F ew'of such rays as are incident directly on the plate strike such faces of the prisms as A, B. such light rays as R, R which first strike the interior of the reflector and are there reflected to the plate,are refracted by the opposite surface of the prism ArB. and are refracted upward from the lamp axis I.

Few if any of such light rays strike the plate so as to be acted upon by side B, C of the prisms of the plate.

The function of the plate is primarily therefore to screen the light rays from the source down to the angle marked screen ing angle. This light is then directed to useful zones. In order to accomplish this result it is essential that the relations between the prism surfaces, reflecting surfaces, inside surfaces of the plate, etc. must be such that no appreciable amount of light can be reflected by surface A, B to the surface B, C or vice versa. Y i

In the preferred form the unit is a combination of prismatic reflector and semi-circular concentric plate, symmetrical with reference to an axis, which makes an angle with the'axis of the lamp. The device is so constructed as to produce a virtual secondary light source so far as light rays falling on the plate'is concerned. The rays from such direct and secondary light sources strilge the inside of the plate at wide angles.

The inner surface ofv the plate E bends the direct. and reflected rays toward each other,

still sufliciently great so that the outer surfaces AB which refract' the reflected. rays will intercept few or none of the direct rays, and the outer surfaces BC which refraot the direct rays will intercept few or none of the Those direct rays which strike surfaces AB will do so at grazing ongles and will be reflected tosurfaces BC with very little change in direction, so that 'On the contrary when they are in turn refracted by surfaces BC they will be emitted in directions very. little higher than that of the typical ray D. The action of reflected rays first striking surfaces BC is entirely similar. to this exce t that they are finally emitted by surfaces A in directions slightly lower than that of typicalrayB.

This combination can be used with re flectors "of material other than mirrored or prism glass and the bottom plate may be of various shapes and obscured by means other than prisms. A highly effective screen is made with-the prismatic construction as above set forth, such prisms having the outer surface etched or sand blasted. In some cases it may be found desirable to use the acid etched or sand blasted screen without the prisms.

The best results, however, have been obtained with the preferred form which is es pecially useful in window lighting.

In modern practice it is customary to place the light sources as near the ceiling of the window as possible, and as close to the glass as possible, so that they will be well out of the range of vision of the observer. When the light sources are so placed it is neces sary to redirect the light down and back from the glass front of the window in order to get the greatest useful effect from the light sources. This is best accomplished by the use of reflectors placed at anangle with the vertical. If, however, the back of the window be open or fitted with mirrors, or if the window has two glass sides, light will be cast into the eyes of an observer standing on the side of the window opposite the light sources, unless some special provision be made for screening thesources on the inner side. If the inner edge of the reflector skirt be extended to accomplish this purpose its sizewill be unduly increased, or the light striking such extension. will be reflected back, toward, and through. the glass front of the window. Transmitting screens such as I have described'will intercept this troublesome light, diffuse same, and emit it in useful directions. At the same time they are of small size and in connection with the reflector form a compact unit.

Having described my invention, what I claim is 1'. A light directing appliance, comprising a reflector having its mouth partially covered with a screen, the reflector being adapted to throw a majority of light rays toward its mouth and the screen having upon its surface prisms directing rays which would otherwise pass out of the mouth beyond a pre-determined angle, one face of such prisms being adapted to receive and direct such direct rays without reflection, the opposite faces acting similarly on such reflected rays. H

2. A light directing appliance, comprising a prismatic reflector having an open mouth partially covered with a screen, the reflector being adapted to throw a majority of light rays toward its mouth and the screen having upon its surface prisms directing rays which would otherwise pass out of the open mouth beyond a predetermined angle, one face of such prisms being adapted to receive and direct such direct rays without reflection, the opposite faces acting similarly on such reflected rays.

3. A light directing appliance, comprising an open mouthed reflector and a screen, the reflector having upon its outer surface double reflecting prisms adapted to send a majority of light rays toward its mouth and the screen partially covering the reflector mouth having upon its surface prisms directing rays which would otherwise pass out of the open mouth beyond a pre-determined angle, one face of such prisms being adapted to receive and direct such direct rays without reflection, the opposite faces acting similarly on such reflected rays.

4. Alight directing appliance comprisinga reflector having an open mouth and partially covered with a screen extending around the rim of the reflector, the reflector being adapted to throw the majority of light rays toward its mouth and the screen having prisms thereon constructed to prevent the transmission of light at angles beyond a predetermined zone of light concentration.

5. A light directing appliance comprising plane of the mouth being inclined to the vertical axis of the reflector and the screen part way around the rim to prevent the transmis sion of light at angles beyond a pre-determined zone of light concentration.

WILLIAM A. DOREY. 

